A specialist drilling machine has been deployed to rescue 40 Indian workers trapped inside a tunnel for more than four days in Uttarakhand state.
It was flown in from Delhi on Wednesday after attempts to drill through the debris using another machine failed.
The machine will help drill a passage so that a pipe can be inserted through which the workers can crawl out.
They have been stuck inside since Sunday, after a landslide caused a portion of the tunnel to collapse.
Authorities told the BBC that they did not want to speculate how long the task of clearing the debris might take, but they were expecting “a positive development” by Thursday evening.
However, federal minister VK Singh on Thursday told reporters that rescue operations could stretch on for another two-three days.
The accident occurred at 05:00 local time (23:30 GMT) on Sunday in the Himalayan state of Uttarakhand. A portion of the Silkyara tunnel, around 200m away from its opening, collapsed while the workers were inside. The mounds of debris cut off oxygen supply to the workers.
The workers are trapped some 200m into the tunnel and are safe, officials said. Rescuers have been providing the men with food, water and oxygen through pipes and are communicating with them through walkie-talkies. However, some reports said that a few of them have been experiencing headaches, anxiety and nausea.
Authorities have denied this and said the workers are not injured.